Electric spot welding arrangement



Feb. 9, 1937. i D. SCIAKY ELECTRIC SPOT WELDING ARRANGEMENT OriginalFiled Aug. 6, 1934 DAV\D SQAKY INVENTQ Patented Feb. 9, 1937 UNITEDSTATES PATENT OFFICE 738,641. 3, 1935, Serial No. 43,304. 1934 3 Claims.

The present invention relates to a device for interrupting the weldingcircuit in a spot welding machine in such manner that the successiveoperations of the various elements are carried out in a simple andreliable manner.

Another object of the present invention is the construction of a devicecomprising electromagnetic control elements which operate in such manneras to avoid shocks during the passage of current which might producetrouble in the control of the elements of the device.

Another object of the invention is to prevent the formation of arcsduring the passage of the friction brushes which are disposed in thewelding circuits.

Another object of the invention is to construct a device which will becapable of producing welds of similar character as compared with oneanother.

, Two forms of the invention are illustrated in the accompanying drawingin which Figure 1 is a diagram illustrating an arrangement according tothe invention.

Figures 2 and 3 are perspective views showing a constructional detail ofthis arrangement.

Figure 4 is a diagram illustrating a modified arrangement according tothe invention.

In the arrangement illustrated in Figures 1 to 3, a discloses theprimary winding and a the secondary winding of a transformer which feedsthe contact electrodes. The primary winding a has sundry leads tappedthereto and is supplied with current under the control of the maincontactor b and of the switch 0. One of the terminals of said primarywinding is connected with a. brush d which makes contact with theperiphery of a disc (1 which is partly conductive and partlynon-conductive and rotated by a synchronous motor I00. On the saidperiphery rests another brush d which is connected with the movablearmature e of a preparatory relay the coil of which is denoted by c.

When the preparatory relay e is energized its armature e moves againstfixed contact e which is connected with the discharge end of the coil e,while when said coil is not energized, armature 6 comes into contactwithfixed contact e which is connected with the welding relay b of themain contactor, said relay being connected, also, with a return line.

The starting pedal j for the welding machine is connected with one ofthe supply conductors I. At rest it contacts with contact spring f whichis connected with preparatory relay e. When this pedal is depressed itcomes against contact Divided and this application October In France May30,

spring I which is connected with the cut-out relay 9 of an auxiliaryrelay having two armatures which are rigidly connected together. The one9 of said armatures is connected with the discharge end of the cut-butrelay g. It is adapted to cooperate with fixed contact 9 which isconnected with a return line. The other armature g cooperates with fixedcontact g, which is connected with the discharge end of preparatoryrelay e.

The discharge end of cut-out relay g and the armature g are connectedwith fixed contacts h and h respectively, which are adapted to coactwith the movable contacts In, h rigidly connected with the maincontactor b. The contact IL -b is closed when the contactor b is open,

while the contact h. -h is established when the contactor b is closed.

Operation When the pedal 1 is depressed, the circuit feeding thepreparatory relay e at rest is interrupted at f Two cases are thenpossible depending on whether the brushes d and d are or are notconnected together, at this moment, by a conducting part of disc (1.

If the brushes are not connected together, the preparatory relay e beingno longer energized, its movable contact e engages fixed contact e Assoon as the brushes d and d are then connected with each other, the maincontactor b will close and remain closed so long as this connectionlasts.

If, on the contrary, the brushes (1 and d are connected with each otherthrough a conducting part of disc 11 when the pedal is depressed,preparatory relay e remains energized and maintains the circuit of thewelding relay b of the contactor open until said connection ceases. Atthis moment the movable contact e engages fixed contact e and as soon asthe brushes (1 and d are connected again, the current passes through band the main contactor closes and remains closed so long as the brushesd and d are con nected through d.

In both cases the contactor b closes, therefore, at the same point of ahalf-cycle and remains closed for the same time, this time beingadjusted by the angular distance which separates the brushes d dfrom'another When closing, the contactor b interrupts the contactbetween h and h and at the same time closes the contact between it and71 The cutout relay g is then fed through h n ,1 and ,f and the contactis established between 9 0 on the one hand and 9 g on the other hand.From this moment the cut-out relay g is again supplied with currentthrough g y. Thus this relay remains energized when the contactor bopens at the end of the welding operation and when the contact is brokenbetween )1 and it. On the other hand, the contactor b, when opening,reestablishes the contact between it and h. This has for its result thate is also supplied with current again and that the circuit of thewelding relay b of the contactor b is therefore interrupted at cTherefore said relay cannot be energized again as long as the pedal isdepressed. When the depression of the pedal ceases the circuit ofcontinuous feeding of e'is re-established at F. At the same time thecircuit of g is broken at f and causes the contacts to open at g and gThus the device is again in the position of rest.

Adjusting of the time of welding The time of closure of the contactor band, consequently, the time during which the welding current passes, canbe made adjustable by making the brush d (Figures 2 and 3) movable. Whenboth brushes are side by side (Figure 3) the closing time of b is amaximum, while it is naught when the angular spacing of both brushescorresponds (Figure 2) to the angle occupied by the conducting part onthe disc d. By making also the contact d movable, it is possible,furthermore, to adjust the point of the halfcycle where the weldingcurrent begins to pass.

Embodiment according to Figure 4 In the embodiment according to Figure 4the disc d coacts with the contactor b for controlling the passage ofthe current in the welding machine. The purpose of this is to diminishthe absolute error of time in the passage of the current by closing theprimary circuit of the welding machine through a contact sliding on d,while avoiding any deterioration of said contact at the breaking pointby effecting the breaking through the contactor.

The primary circuit passes through the body of disc d, a brush i and themain contactor b. Another brush (1 rests on disc (1. It is shifted abouta certain angle with respect to i in the opposite direction to therotation of the disc d. This angle is a function of the constant of timeof the contactor. The brush d is connected with the fixed contacts e eof a relay equivalent to the relays e---e of the unit according toFigure 1. In this case both movable contacts 6 0 are connected, one withthe outlet of the preparatory relay e, and the other at one end of thewelding relay b of the main contactor. When the welding machine is atrest, the preparatory relay e is supplied with current withoutinterruption, its circuit is closed through I and the pedal 1, e, e isthen in contact with e while the contact is broken between c and c Whenthe pedal is depressed the permanent feeding circuit of the preparatoryrelay eis broken.

Two cases are then also possible.

(1) The brush at is at this moment on a nonconducting part of disc d.Preparatory relay e is then no longer energized, the contact is brokenbetween e and e and established between e and c Consequently, as soon asthe conducting part of d comes against the brush a, welding relay bl isenergized and the contactor closes. However, the circuit of the weldingmachine is closed only afterwards, when the conducting part of the discd comes against the brush 2.

For the breaking the non-conducting part of disc :2 comes first againstthe brushd This has -for its result that the energization circuit of bis broken and that the contactor opens, consequently, before theinsulating part of disc (1 has come against the brush 2'. Thus thecurrent is already interrupted when the sliding contact opens.

(2) If, at the moment of the depression of the pedal, the brush d is incontact with a conducting part of d, the preparatory relay e remainsenergized through e e (1 d. Thus the circuit of b remains broken until(1 is engaged by the nonconducting part of d and so long as it is notengaged by its conducting part. Then -the device operates as in theforegoing case.

I claim:

1. In a commutator device for feeding the electrodes of a weldingmachine, a starting pedal, a preparatory relay controlled by said pedal,feeding means for continuously feeding said preparatory relay during therest position thereof, a cutout relay for restoring energization of thepreparatory relay as soon as a Weld has been completed, a synchronousmotor fed from a current source, a rotary commutator provided withcontacts controlled by the synchronous motor and controlling thepreparatory relay, a welding relay controlled by the preparatory relay,and controlling the welding circuit.

2. In a commutator device for feeding the electrodes of a weldingmachine, a starting pedal, a preparatory relay controlled by said pedal,feeding means for continuously feeding said preparatory relay during therest position thereof, a cutout relay for restoring energization of thepreparatory relay as soon as a weld has been completed, a synchronousmotor fed by a current source, a disc consisting of an insulatingportion and a conductive portion, said disc being rotated by saidsynchronous motor, two brushes in engagement with said disc andadjustable with respect to each other, the first brush being connectedto a current source, whereas the second brush is connected to thepreparatory relay, a welding relay controlled by the preparatory relayand controlling the welding circuit.

3. In a commutator device for feeding the electrodes of a weldingmachine, a starting pedal, a preparatory relay controlled by said pedal,feeding means for continuously feeding said preparatory relay during therest position thereof, a cut-out relay for restoring energization of thepreparatory relay as soon as a weld has been completed, a synchronousmotor fed by a current source, a rotary commutator operated by saidsynchronous motor and disposed directly in the welding circuit, saidcommutator carrying a brush, the latter being connected to thepreparatory relay and a second brush disposed in the welding circuit, awelding relay comprising a contact disposed in series with the saidsecond brush of the rotary commutator.

DAVID SCIAKY.

